Sarunas Verner

Gravitational Waves from Long Strings and Loops

Christos Litos, Sarunas Verner, Wei Xue +1

We compute the gravitational wave spectrum produced by a global cosmic string network in the scaling regime. The spectrum naturally divides at the string correlation length into in…

Axion isocurvature and the model-building problem of low-scale inflation

Sarunas Verner

The pre-inflationary QCD axion is often said to require low-scale inflation. We derive a general isocurvature bound for a light axion with a scale-invariant spectrum, treating its…

Reheating in No-Scale Models of Inflation

Ignatios Antoniadis, John Ellis, Dimitri V. Nanopoulos +2

Analogously to the suppression of inflaton decays into conformally-coupled scalar fields in the original Starobinsky $R + R^{2}$ model of inflation, inflaton decays to Standard Model…

Cosmological gravitational particle production in multifield inflation

Edward W. Kolb, Sarunas Verner, Jingyuan Wang

We study cosmological gravitational particle production (CGPP) of dark matter in two-field inflationary backgrounds with both flat and curved field-space geometries. As a concrete…

Gravitational Waves from Matter Perturbations of Spectator Scalar Fields

Marcos A. G. Garcia, Angel Garcia-Vega, Sarunas Verner

We compute the stochastic gravitational wave background sourced at second order by a spectator scalar field $χ$ coupled to the inflaton $ϕ$ through a portal interaction $σ ϕ^{2} χ^{2}$ a…

Gravitational Production of Massive Spin-2 Particles During Reheating

Sarunas Verner

We study the minimal gravitational portal for a massive spin-2 dark matter candidate $X_{μν}$ produced during perturbative reheating. The dark sector couples to the visible sector…

Gravitational Waves from Isocurvature Perturbations of Spectator Scalar Fields

Marcos A. G. Garcia, Sarunas Verner

We present a mechanism for gravitational wave (GW) production from isocurvature perturbations in spectator scalar fields during inflation. These energetically subdominant fields de…

Constraints on Attractor Models of Inflation and Reheating from Planck, BICEP/Keck, ACT DR6, and SPT-3G Data

John Ellis, Marcos A. G. Garcia, Keith A. Olive +1

We analyze the latest cosmic microwave background (CMB) constraints on the scalar spectral index $n_{s}$ and tensor-to-scalar ratio $r$ from Planck 2018, BICEP/Keck 2018, the Atacama…

Gravitational Waves from Spectator Scalar Fields

Marcos A. G. Garcia, Sarunas Verner

We propose a novel mechanism for gravitational wave (GW) production sourced by spectator scalar fields during inflation. These fields, while not driving cosmic expansion, generate…

The Electroweak Sphaleron Revisited: II. Study of Decay Dynamics

Konstantin T. Matchev, Sarunas Verner

We present a comprehensive analysis of electroweak sphaleron decay dynamics, employing both analytical techniques and high-resolution numerical simulations. Using a spherically sym…

The Electroweak Sphaleron Revisited: I. Static Solutions, Energy Barrier, and Unstable Modes

Konstantin T. Matchev, Sarunas Verner

The electroweak sphaleron is a static, unstable solution of the Standard Model classical field equations, representing the energy barrier between topologically distinct vacua. In t…

Scalar Field Fluctuations and the Production of Dark Matter

Marcos A. G. Garcia, Wenqi Ke, Yann Mambrini +2

One of the simplest possible candidates for dark matter is a stable scalar singlet beyond the Standard Model. If its mass is below the Hubble scale during inflation, long-wavelengt…

Nonminimal Superheavy Dark Matter

Sarunas Verner

We investigate the gravitational production of superheavy scalar fields with nonminimal coupling during and after inflation. We derive analytical approximations using the mode func…

Inflaton Production of Scalar Dark Matter through Fluctuations and Scattering

Gongjun Choi, Marcos A. G. Garcia, Wenqi Ke +3

We study the effects on particle production of a Planck-suppressed coupling between the inflaton and a scalar dark matter candidate, $χ$ . In the absence of this coupling, the domin…

Astrometric Detection of Ultralight Dark Matter

Jeff A. Dror, Sarunas Verner

Ultralight dark matter induces time-dependent perturbations in the spacetime metric, enabling its gravitational direct detection. In this work, we propose using astrometry to detec…

Gravitational Production of Heavy Particles during and after Inflation

Davide Racco, Sarunas Verner, Wei Xue

We investigate the gravitational production of a scalar field $χ$ with a mass exceeding the Hubble scale during inflation $m_{χ} ≳ H_{I}$ , employing both analytical and numerical…

Inflaton decay in No-Scale Supergravity and Starobinsky-like models

Yohei Ema, Marcos A. G. Garcia, Wenqi Ke +2

We consider the decay of the inflaton in Starobinsky-like models arising from either an $R + R^{2}$ theory of gravity or $N = 1$ no-scale supergravity models. If Standard Model matter is…

Exploring the Truth and Beauty of Theory Landscapes with Machine Learning

Konstantin T. Matchev, Katia Matcheva, Pierre Ramond +1

Theoretical physicists describe nature by i) building a theory model and ii) determining the model parameters. The latter step involves the dual aspect of both fitting to the exist…

The Role of Vectors in Reheating

Marcos A. G. Garcia, Kunio Kaneta, Wenqi Ke +3

We explore various aspects concerning the role of vector bosons during the reheating process. Generally, reheating occurs during the period of oscillations of the inflaton condensa…

Seeking Truth and Beauty in Flavor Physics with Machine Learning

Konstantin T. Matchev, Katia Matcheva, Pierre Ramond +1

The discovery process of building new theoretical physics models involves the dual aspect of both fitting to the existing experimental data and satisfying abstract theorists' crite…

Identifying the Group-Theoretic Structure of Machine-Learned Symmetries

Roy T. Forestano, Konstantin T. Matchev, Katia Matcheva +3

Deep learning was recently successfully used in deriving symmetry transformations that preserve important physics quantities. Being completely agnostic, these techniques postpone t…

Gravitational Production of Spin-3/2 Particles During Reheating

Kunio Kaneta, Wenqi Ke, Yann Mambrini +2

We compute the density of a spin- $\frac{3}{2}$ particle, the raritron, produced at the end of inflation due to gravitational interactions. We consider a background inflaton condensate…